Ustc-1280 Finding shortest path 网络流

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题目链接
#include <stdio.h>#include <string.h>#include<functional>#include <queue>#include <algorithm>using namespace std;const int maxn = 2005;const int inf = 1<<30;int n,m,pos,Pos;int Start,End;struct node{int to,w,c,next;}edge[maxn*20];struct node1{int to,c,pos,next;}Edge[maxn*20];int Head[maxn],head[maxn],dis[maxn];bool vis[maxn];void addedge( int u,int v,int w,int c )  {  edge[++pos].to = v; edge[pos].w = w; edge[pos].c = c;    edge[pos].next = head[u]; head[u] = pos;   }void addEdge( int u,int v,int c ){Edge[++Pos].to = v; Edge[Pos].c = c; Edge[Pos].pos = Pos;    Edge[Pos].next = Head[u]; Head[u] = Pos;  Edge[++Pos].to = u; Edge[Pos].c = 0;  Edge[Pos].pos = Pos;    Edge[Pos].next = Head[u]; Head[u] = Pos;   }vector<int>path[maxn];typedef pair<int,int>pii; void Dijstra( int s ){priority_queue<pii,vector<pii>,greater<pii> >que;      memset( vis,0,sizeof(vis) );      for( int i = 1; i <= n; i ++ )          dis[i] = inf;      dis[s] = 0;    que.push( make_pair(dis[s],s) );while( !que.empty() ){pii u = que.top(); que.pop();int v = u.second;if( vis[v] )continue;vis[v] = 1;for( int i = head[v]; i != -1; i = edge[i].next  ){node tmp = edge[i];if( dis[tmp.to] > dis[v] + tmp.w ){dis[tmp.to] = dis[v] + tmp.w;que.push( make_pair( dis[tmp.to],tmp.to ) );}}}}bool dinic_bfs( int start,int end )  {      memset(vis,0,sizeof(vis));      memset(dis,0,sizeof(dis));            vis[start] = true;      dis[start] = 0;      queue<int>q;      q.push(start);      while( !q.empty() )      {          int e = q.front();          q.pop();          if( e == end )              return true;  for( int i = Head[e]; i != -1; i = Edge[i].next )          {  if( !vis[ Edge[i].to] &&  Edge[i].c )              {                  vis[ Edge[i].to] = true;  q.push( Edge[i].to );  dis[Edge[i].to] = dis[e] + 1;              }          }      }      return false;  }    int dinic_dfs( int start,int maxf,int end )  {      if( start==end )          return maxf;      int ans = 0,flow;  for( int i = Head[start]; i != -1; i = Edge[i].next )      {  if( dis[Edge[i].to] == dis[start] + 1 )          {  flow = dinic_dfs( Edge[i].to,Edge[i].c < maxf?Edge[i].c:maxf,end );              ans += flow;              maxf -= flow;  Edge[i].c -= flow;              Edge[Edge[i].pos^1].c +=flow;              if( maxf==0 )                  break;          }      }      return ans;  }    int Dinic( int start,int end )  {      int ans = 0;      while( dinic_bfs( start,end ) )          ans += dinic_dfs( start, inf ,end );      return ans;  }void dfs( int x ){vis[x] = 1;for( int i = head[x]; i != -1; i = edge[i].next ){if( dis[edge[i].to] + edge[i].w == dis[x] ){addEdge( x,edge[i].to,edge[i].c );if( vis[edge[i].to] ) continue;dfs( edge[i].to );}}}void Init(){pos = 0;Pos = 0;for( int i = 0; i <= n; i ++ ){head[i] = -1;Head[i] = -1;}}int main(){#ifndef ONLINE_JUDGE      freopen("data.txt","r",stdin);      #endif  int cas = 1,x,y,w,c;    while( scanf("%d%d",&n,&m) != EOF,(n||m) ){Init();scanf("%d%d",&Start,&End);for( int i = 0; i < m; i ++ ){scanf("%d%d%d%d",&x,&y,&w,&c);addedge( x,y,w,c );addedge( y,x,w,c );}Dijstra( Start );memset( vis,0,sizeof(vis) );dfs( End );printf("Case %d: %d\n",cas ++,Dinic( End,Start ));}    return 0;}
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